Power spectrum density (PSD) is a positive real function of a frequency variable associated with a stationary stochastic process describing how the power of a signal or time series is distributed with frequency [1]. The analysis of PSD known as Power Spectral Analysis (PSA) provides a non-invasive means of accessing the physiological and pathological status of a person and is becoming a ubiquitous tool in the diagnosis, prediction and monitoring of various cardiac and brain malfunctions [2-6]. Usually the total low frequency power (LFP) between 0.04 and 0.15 Hz and the total high frequency power (LFP) between 0.15 and 0.4 Hz of cardiac spectra along with their ratio (HFP:LFP) are used as quantitative indicators of various cardiac diseases (i.e., episodic hypertension, sinus tachycardia, bradyarrhythmia, Guillain-Barre syndrome, etc.). Similarly the total power calculated within 3.5-7.5 Hz, 7.5-12.5 Hz and at 12.5 Hz of brain spectra can help in monitoring the brain activity and in diagnosing of epileptic seizures.
By considering the fact that cardiovascular diseases are already responsible for one third of the deaths worldwide, one can easily realize the high value of such a tool in health monitoring [12]. After all the rapid aging of population and prevalence of unhealthy lifestyles is expected to further increase the importance of such applications and need for their integration in our daily portable devices in the near future. Integrating PSA systems within wearable, miniaturized and wireless sensors able to measure and wirelessly report cardiac signals to tele-health providers would enable the required personalized, real-time and long term ambulatory monitoring of chronic patients, its seamless integration with the patient's medical record and its coordination with nursing/medical support. However the high complexity of such applications may hinder their widespread use in particular in portable devices, thus making necessary to devise methods that can reduce their complexity with minimum/no impact on the disease detection capability.